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exim.12268
CVE-2019-13917.patch
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File CVE-2019-13917.patch of Package exim.12268
Index: exim-4.88/doc/ChangeLog =================================================================== --- exim-4.88.orig/doc/ChangeLog +++ exim-4.88/doc/ChangeLog @@ -117,6 +117,8 @@ JH/29 Fix the connection_reject log sele JH/30 Bug 1897: fix callouts connection fallback from TLS to cleartext. +JH/31 Avoid re-expansion in ${sort } expansion. (CVE-2019-13917) + PP/01 Changed default Diffie-Hellman parameters to be Exim-specific, created by me. Added RFC7919 DH primes as an alternative. Index: exim-4.88/doc/cve-2019-13917 =================================================================== --- /dev/null +++ exim-4.88/doc/cve-2019-13917 @@ -0,0 +1,46 @@ +CVE ID: CVE-2019-13917 +OVE ID: OVE-20190718-0006 +Date: 2019-07-18 +Credits: Jeremy Harris +Version(s): 4.85 up to and including 4.92 +Issue: A local or remote attacker can execute programs with root + privileges - if you've an unusual configuration. See below. + +Conditions to be vulnerable +=========================== + +If your configuration uses the ${sort } expansion for items that can be +controlled by an attacker (e.g. $local_part, $domain). The default +config, as shipped by the Exim developers, does not contain ${sort }. + +Details +======= + +The vulnerability is exploitable either remotely or locally and could +be used to execute other programs with root privilege. The ${sort } +expansion re-evaluates its items. + +Mitigation +========== + +Do not use ${sort } in your configuration. + +Fix +=== + +Download and build a fixed version: + + Tarballs: http://ftp.exim.org/pub/exim/exim4/ + Git: https://github.com/Exim/exim.git + - tag exim-4.92.1 + - branch exim-4.92+fixes + +The tagged commit is the officially released version. The +fixes branch +isn't officially maintained, but contains useful patches *and* the +security fix. + +If you can't install the above versions, ask your package maintainer for +a version containing the backported fix. On request and depending on our +resources we will support you in backporting the fix. (Please note, +that Exim project officially doesn't support versions prior the current +stable version.) Index: exim-4.88/src/expand.c =================================================================== --- exim-4.88.orig/src/expand.c +++ exim-4.88/src/expand.c @@ -2114,6 +2114,54 @@ return ret; +/************************************************/ +/* Return offset in ops table, or -1 if not found. +Repoint to just after the operator in the string. +Argument: + ss string representation of operator + opname split-out operator name +*/ + +static int +identify_operator(const uschar ** ss, uschar ** opname) +{ +const uschar * s = *ss; +uschar name[256]; + +/* Numeric comparisons are symbolic */ + +if (*s == '=' || *s == '>' || *s == '<') + { + int p = 0; + name[p++] = *s++; + if (*s == '=') + { + name[p++] = '='; + s++; + } + name[p] = 0; + } + +/* All other conditions are named */ + +else + s = read_name(name, sizeof(name), s, US"_"); +*ss = s; + +/* If we haven't read a name, it means some non-alpha character is first. */ + +if (!name[0]) + { + expand_string_message = string_sprintf("condition name expected, " + "but found \"%.16s\"", s); + return -1; + } +if (opname) + *opname = string_copy(name); + +return chop_match(name, cond_table, nelem(cond_table)); +} + /************************************************* * Read and evaluate a condition * @@ -2144,6 +2192,7 @@ BOOL sub2_honour_dollar = TRUE; int i, rc, cond_type, roffset; int_eximarith_t num[2]; struct stat statbuf; +uschar * opname; uschar name[256]; const uschar *sub[10]; @@ -2156,37 +2205,7 @@ for (;;) if (*s == '!') { testfor = !testfor; s++; } else break; } -/* Numeric comparisons are symbolic */ - -if (*s == '=' || *s == '>' || *s == '<') - { - int p = 0; - name[p++] = *s++; - if (*s == '=') - { - name[p++] = '='; - s++; - } - name[p] = 0; - } - -/* All other conditions are named */ - -else s = read_name(name, 256, s, US"_"); - -/* If we haven't read a name, it means some non-alpha character is first. */ - -if (name[0] == 0) - { - expand_string_message = string_sprintf("condition name expected, " - "but found \"%.16s\"", s); - return NULL; - } - -/* Find which condition we are dealing with, and switch on it */ - -cond_type = chop_match(name, cond_table, nelem(cond_table)); -switch(cond_type) +switch(cond_type = identify_operator(&s, &opname)) { /* def: tests for a non-empty variable, or for the existence of a header. If yield == NULL we are in a skipping state, and don't care about the answer. */ @@ -2505,7 +2524,7 @@ switch(cond_type) { if (i == 0) goto COND_FAILED_CURLY_START; expand_string_message = string_sprintf("missing 2nd string in {} " - "after \"%s\"", name); + "after \"%s\"", opname); return NULL; } sub[i] = expand_string_internal(s+1, TRUE, &s, yield == NULL, @@ -2517,7 +2536,7 @@ switch(cond_type) conditions that compare numbers do not start with a letter. This just saves checking for them individually. */ - if (!isalpha(name[0]) && yield != NULL) + if (!isalpha(opname[0]) && yield != NULL) if (sub[i][0] == 0) { num[i] = 0; @@ -2831,7 +2850,7 @@ switch(cond_type) uschar *save_iterate_item = iterate_item; int (*compare)(const uschar *, const uschar *); - DEBUG(D_expand) debug_printf("condition: %s\n", name); + DEBUG(D_expand) debug_printf("condition: %s\n", opname); tempcond = FALSE; compare = cond_type == ECOND_INLISTI @@ -2870,14 +2889,14 @@ switch(cond_type) if (*s != '{') /* }-for-text-editors */ { expand_string_message = string_sprintf("each subcondition " - "inside an \"%s{...}\" condition must be in its own {}", name); + "inside an \"%s{...}\" condition must be in its own {}", opname); return NULL; } if (!(s = eval_condition(s+1, resetok, subcondptr))) { expand_string_message = string_sprintf("%s inside \"%s{...}\" condition", - expand_string_message, name); + expand_string_message, opname); return NULL; } while (isspace(*s)) s++; @@ -2887,7 +2906,7 @@ switch(cond_type) { /* {-for-text-editors */ expand_string_message = string_sprintf("missing } at end of condition " - "inside \"%s\" group", name); + "inside \"%s\" group", opname); return NULL; } @@ -2919,7 +2938,7 @@ switch(cond_type) int sep = 0; uschar *save_iterate_item = iterate_item; - DEBUG(D_expand) debug_printf("condition: %s\n", name); + DEBUG(D_expand) debug_printf("condition: %s\n", opname); while (isspace(*s)) s++; if (*s++ != '{') goto COND_FAILED_CURLY_START; /* }-for-text-editors */ @@ -2940,7 +2959,7 @@ switch(cond_type) if (!(s = eval_condition(sub[1], resetok, NULL))) { expand_string_message = string_sprintf("%s inside \"%s\" condition", - expand_string_message, name); + expand_string_message, opname); return NULL; } while (isspace(*s)) s++; @@ -2950,7 +2969,7 @@ switch(cond_type) { /* {-for-text-editors */ expand_string_message = string_sprintf("missing } at end of condition " - "inside \"%s\"", name); + "inside \"%s\"", opname); return NULL; } @@ -2962,11 +2981,11 @@ switch(cond_type) if (!eval_condition(sub[1], resetok, &tempcond)) { expand_string_message = string_sprintf("%s inside \"%s\" condition", - expand_string_message, name); + expand_string_message,opname); iterate_item = save_iterate_item; return NULL; } - DEBUG(D_expand) debug_printf("%s: condition evaluated to %s\n", name, + DEBUG(D_expand) debug_printf("%s: condition evaluated to %s\n", opname, tempcond? "true":"false"); if (yield != NULL) *yield = (tempcond == testfor); @@ -3059,19 +3078,20 @@ switch(cond_type) /* Unknown condition */ default: - expand_string_message = string_sprintf("unknown condition \"%s\"", name); - return NULL; + if (!expand_string_message || !*expand_string_message) + expand_string_message = string_sprintf("unknown condition \"%s\"", opname); + return NULL; } /* End switch on condition type */ /* Missing braces at start and end of data */ COND_FAILED_CURLY_START: -expand_string_message = string_sprintf("missing { after \"%s\"", name); +expand_string_message = string_sprintf("missing { after \"%s\"", opname); return NULL; COND_FAILED_CURLY_END: expand_string_message = string_sprintf("missing } at end of \"%s\" condition", - name); + opname); return NULL; /* A condition requires code that is not compiled */ @@ -3081,7 +3101,7 @@ return NULL; !defined(SUPPORT_CRYPTEQ) || !defined(CYRUS_SASLAUTHD_SOCKET) COND_FAILED_NOT_COMPILED: expand_string_message = string_sprintf("support for \"%s\" not compiled", - name); + opname); return NULL; #endif } @@ -3793,6 +3813,54 @@ return x; +/************************************************/ +/* Comparison operation for sort expansion. We need to avoid +re-expanding the fields being compared, so need a custom routine. +Arguments: + cond_type Comparison operator code + leftarg, rightarg Arguments for comparison +Return true iff (leftarg compare rightarg) +*/ + +static BOOL +sortsbefore(int cond_type, BOOL alpha_cond, + const uschar * leftarg, const uschar * rightarg) +{ +int_eximarith_t l_num, r_num; + +if (!alpha_cond) + { + l_num = expanded_string_integer(leftarg, FALSE); + if (expand_string_message) return FALSE; + r_num = expanded_string_integer(rightarg, FALSE); + if (expand_string_message) return FALSE; + + switch (cond_type) + { + case ECOND_NUM_G: return l_num > r_num; + case ECOND_NUM_GE: return l_num >= r_num; + case ECOND_NUM_L: return l_num < r_num; + case ECOND_NUM_LE: return l_num <= r_num; + default: break; + } + } +else + switch (cond_type) + { + case ECOND_STR_LT: return Ustrcmp (leftarg, rightarg) < 0; + case ECOND_STR_LTI: return strcmpic(leftarg, rightarg) < 0; + case ECOND_STR_LE: return Ustrcmp (leftarg, rightarg) <= 0; + case ECOND_STR_LEI: return strcmpic(leftarg, rightarg) <= 0; + case ECOND_STR_GT: return Ustrcmp (leftarg, rightarg) > 0; + case ECOND_STR_GTI: return strcmpic(leftarg, rightarg) > 0; + case ECOND_STR_GE: return Ustrcmp (leftarg, rightarg) >= 0; + case ECOND_STR_GEI: return strcmpic(leftarg, rightarg) >= 0; + default: break; + } +return FALSE; /* should not happen */ +} + + /************************************************* * Expand string * *************************************************/ @@ -5898,9 +5966,10 @@ while (*s != 0) case EITEM_SORT: { + int cond_type; int sep = 0; const uschar *srclist, *cmp, *xtract; - uschar *srcitem; + uschar * opname, * srcitem; const uschar *dstlist = NULL, *dstkeylist = NULL; uschar * tmp; uschar *save_iterate_item = iterate_item; @@ -5920,6 +5989,25 @@ while (*s != 0) goto EXPAND_FAILED_CURLY; } + if ((cond_type = identify_operator(&cmp, &opname)) == -1) + { + if (!expand_string_message) + expand_string_message = string_sprintf("unknown condition \"%s\"", s); + goto EXPAND_FAILED; + } + switch(cond_type) + { + case ECOND_NUM_L: case ECOND_NUM_LE: + case ECOND_NUM_G: case ECOND_NUM_GE: + case ECOND_STR_GE: case ECOND_STR_GEI: case ECOND_STR_GT: case ECOND_STR_GTI: + case ECOND_STR_LE: case ECOND_STR_LEI: case ECOND_STR_LT: case ECOND_STR_LTI: + break; + + default: + expand_string_message = US"comparator not handled for sort"; + goto EXPAND_FAILED; +} + while (isspace(*s)) s++; if (*s++ != '{') { @@ -5963,10 +6051,9 @@ while (*s != 0) while ((srcitem = string_nextinlist(&srclist, &sep, NULL, 0))) { - uschar * dstitem; + uschar * srcfield, * dstitem; uschar * newlist = NULL; uschar * newkeylist = NULL; - uschar * srcfield; DEBUG(D_expand) debug_printf("%s: $item = \"%s\"\n", name, srcitem); @@ -5987,26 +6074,16 @@ while (*s != 0) while ((dstitem = string_nextinlist(&dstlist, &sep, NULL, 0))) { uschar * dstfield; - uschar * expr; - BOOL before; /* field for comparison */ if (!(dstfield = string_nextinlist(&dstkeylist, &sep, NULL, 0))) goto sort_mismatch; - /* build and run condition string */ - expr = string_sprintf("%s{%s}{%s}", cmp, srcfield, dstfield); + /* String-comparator names start with a letter; numeric names do not */ - DEBUG(D_expand) debug_printf("%s: cond = \"%s\"\n", name, expr); - if (!eval_condition(expr, &resetok, &before)) - { - expand_string_message = string_sprintf("comparison in sort: %s", - expr); - goto EXPAND_FAILED; - } - - if (before) - { + if (sortsbefore(cond_type, isalpha(opname[0]), + srcfield, dstfield)) + { /* New-item sorts before this dst-item. Append new-item, then dst-item, then remainder of dst list. */
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